(1) Field of the Invention:
The present invention relates to a one-package inorganic binder composition. More particularly, the present invention relates to an inorganic binder composition which contains a binder component and a curing agent component in one package and which is used as a binder in various fields by addition of water on application. Especially, the present invention relates to an inorganic binder composition which is excellent in the storage stability though it is in the form of one package and also is excellent in the properties required for binders, such as the adhesive force and water resistance.
(2) Description of the Prior Art:
As the inorganic coating composition, there has been used a composition comprising as the main component a water-soluble silicate, such as so-called water glass. A water-soluble silicate such as water glass forms an aqueous solution having a high close contact property and a high adhesion, and this aqueous solution can easily be applied to a substrate to be bonded or coated. However, this aqueous solution is defective in that a long time is necessary for curing the coating, the form-retaining property or dimension stability of the coating is poor and so-called sagging is readily caused, and the resulting cured coating is insufficient in such properties as water resistance, weatherability and toughness. As means for improving these properties, there has widely been adopted method in which an acid or acidic salt is added as a curing agent to an aqueous solution of a water-soluble silicate. However, since this curing agent has a high reactivity with the silicate as the binder, premature gelation of the silicate or heterogeneous partial gelation is readily caused, the adaptability to the bonding or coating operation is not good, and the resulting cured coating is still insufficient in the water resistance, toughness and weatherability.
As means for preventing premature or partial gelation in a binder composition comprising an alkali metal silicate binder and an inorganic phosphate curing agent, we previously proposed a method in which a curing agent composed mainly of silicon polyphosphate having a property of gradually releasing phosphoric acid or an alkali metal salt thereof is used as the curing agent to prolong the pot life of the binder composition (see the specification U.S. Pat. No. 4,018,616).
This silicon polyphosphate type curing agent gives a much longer pot life to an alkali metal silicate binder than the conventional phosphoric acid type curing agent. However, this binder composition is defective in that a liquid (an aqueous solution of an alkali metal silicate) and a powder (silicon polyphosphate) should be metered independently and mixed on application.